Color layer forming method

ABSTRACT

For each of colored resists, a resist coating step of coating a washed substrate with the colored resist, a reduced-pressure drying and temporary baking step of evaporating solvent contained in the colored resist, an exposing step of printing a pattern in the colored resist, a developing the printed pattern and a photo-curing and temporary post-baking step of hardening a surface portion of the resist to a hardness level, in which there is no defect of the printed colored resist pattern occurs in a coating step and a developing step, which are performed later, are repeated. In forming a last colored resist, a normal baking step of simultaneously hardening all of the coated colored resist patterns is performed, instead of the photo-curing and temporary post-baking step.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for forming a colorlayer for use in a color filter, etc., and, in particular, the presentinvention relates to a method for forming a color layer, which includesa plurality of colored resists, on a substrate.

[0003] 2. Description of the Related Art

[0004] One of important conditions required in a colored resisthardening step in a fabrication method for forming an optical colorfilter used in a flat display panel such as a plasma display panel or ina camera, etc., is that the colored resist hardening step does not causedefect or abnormality in a resist pattern to be formed in a later step.

[0005] A conventional procedure for forming a color filter on asubstrate will be described with reference to FIG. 6.

[0006] After a pre-cleaning step to be performed in order to wash awayextraneous substances adhered to the substrate (step S31, step S38, stepS45), a resist coating step (step S32, step S39, step S46) for coatingthe substrate with a light-sensitive colored resist is performed.Thereafter, a drying step (step S33, step S40, step S47) underreduced-pressure for evaporating and removing solvent contained in theresist and a temporary baking step (step S34, step S41, step S48) areperformed. Subsequent to the temporary baking step, an exposing step(step S35, step S42, step S49) for printing a pattern in the resist isperformed and then a developing step (step S36, step S43, step S50) fordeveloping the printed pattern is performed. Thereafter, a normal bakingstep (step S37, step S44, step S51) for sufficiently heating thedeveloped pattern formed on the substrate to completely evaporatesolvent contained in the resist and thermally harden the patternedresist by a hotplate or an oven is performed. The above series of thesteps is performed every time when each of the first, second and thirdprimary colored filter patterns is formed.

[0007] However, in the above mentioned fabrication procedure, the normalbaking is performed at a temperature of 200˜230° C. for about 1 hour.Therefore, considering a time for heating the substrate up to the bakingtemperature and a time for cooling the substrate, a required time in thenormal baking step becomes 3˜4 hours, which is the longest time in thecolor filter fabrication procedure. Therefore, there is a problem inview of improvement of producibility of color filter.

[0008] In order to solve this problem, JPH11-337724A, for example,discloses a technique in which the hardening step of the resist isperformed in a temporary post-baking step under a generous conditioncompared with the condition of the normal baking step.

[0009] According to the technique disclosed in JPH11-337724A, atemporary post-baking step, that is, a half-hardening step, forthermally hardening the resist pattern to a hardness level, in which theresist pattern is not peeled off in the succeeding developing step, isused in lieu of the normal baking step for complete hardening the resistunder the above mentioned condition for every color layer. However,after the last color layer of three primary color layers is patterned,the normal baking of the three color layers is performed at one time.Thus, the disclosed method is effective in reducing a time required forthe resist hardening step of the color layer forming method includingthe pattern formation by coating the substrate with the resist on thesubstrate and repeating the pattern formation for the primary colors.

[0010] However, a further reduction of time required for the color layerforming method is requested. It may be thought that further reduction ofthe required time is possible by not further reducing a time requiredfor the temporary post-baking step but slightly increasing thetemperature of the temporary post-baking step. However, according toexperiments conducted by the present inventors, it has been found thatthe surface hardness of the color layer resist becomes insufficient anddeveloping agent in the subsequent step soaks into the color layer.

SUMMARY OF THE INVENTION

[0011] Consequently, an object of the present invention is to provide acolor layer forming method, which is featured by that a half-hardeningstep is performed by combining a surface hardening step using light anda surface hardening step for hardening a surface of the color layer onthe side of the substrate, that is, an interface side surface of thecolor layer, by heat from the substrate. With the color layer formingmethod, it is possible to substantially reduce a time required for thehardening step, resulting in high producibility of a color filter.

[0012] Another object of the present invention is to provide a colorfilter forming method by utilizing the color layer forming method.

[0013] Another object of the present invention is to provide a colorfilter fabricated by using the color filter forming method.

[0014] In order to achieve the above objects, the color layer formingmethod for forming a color layer including a plurality of coloredresists on a substrate according to the present invention comprises, forevery colored resist other than the last colored resist of the pluralityof the colored resists, the step of coating the substrate, which iswashed, with the colored resist, the step of drying the substrate underreduced-pressure condition to evaporate solvent contained in the coloredresist and temporarily baking the substrate, the step of exposing thecolored resist to print a pattern in the latter colored resist, the stepof developing the pattern, the step of photo-curing and temporarilybaking the colored resist pattern to a hardness level in which there isno defect of a printed colored resist pattern in a resist printing stepand a developing step, which are performed later, the step of repeatingthe above mentioned steps and, for the last colored resist, the step ofcoating the substrate, which is washed, with the last colored resist,the step of drying the substrate under reduced-pressure condition toevaporate solvent contained in the last colored resist and temporarilybaking the substrate, the step of exposing the last colored resist toprint a pattern in the latter colored resist, the step of developing thecolored resist pattern and the step of normally baking all of the coatedcolored resist patterns simultaneously.

[0015] The color filter forming method for forming a color layerincluding a plurality of colored resists and a light shield layer formedof a light sensitive black resist on a substrate according to thepresent invention comprises, for every colored resist of the pluralityof the colored resists other than the last colored resist thereof, thestep of coating the washed substrate with the colored resist, the stepof drying the substrate under reduced-pressure condition to evaporatesolvent contained in the colored resist and temporarily baking thesubstrate, the step of exposing the colored resist to print a resistpattern of the colored resist, the step of developing the pattern, thestep of photo-curing and temporarily baking the colored resist patternto a hardness level in which there is no defect of a printed coloredresist pattern in a resist printing step and a developing step, whichare performed later, the step of repeating the above mentioned stepsand, for the last colored resist, the step of coating the colored resiston the washed substrate, the step of drying the substrate underreduced-pressure condition to evaporate solvent contained in the coloredresist, the step of temporarily baking the substrate, the step ofexposing the colored resist to print a pattern of the colored resist,the step of developing the colored resist pattern, the step of normallybaking all of the colored resist patterns simultaneously.

[0016] The color filter forming method for forming a color layerincluding a plurality of color layers and a transparent organicinterlayer film formed of a negative type resist on a substrateaccording to the present invention comprises, for every colored resistof the plurality of the colored resists other than the last coloredresist, the step of coating the washed substrate with the coloredresist, the step of drying the substrate under reduced-pressurecondition to evaporate solvent contained in the colored resist, the stepof temporarily baking the substrate, the step of exposing the coloredresist to print a pattern in the colored resist, the step of developingthe pattern, the step of photo-curing and temporarily baking the coloredresist pattern to a hardness level in which there is no defect of aprinted colored resist pattern in a resist printing step and adeveloping step, which are performed later, the step of repeating theabove mentioned steps and, for the last transparent organic interlayerfilm, the step of coating the washed substrate with the colored resist,the step of drying the substrate under reduced-pressure condition toevaporate solvent contained in the colored resist, the step oftemporarily baking the substrate, the step of exposing the coloredresist to print a pattern of the colored resist, the step of developingthe colored resist pattern, the step of normally baking all of thecoated colored resist patterns and the transparent organic interlayerfilms simultaneously.

[0017] In the present invention, it is possible to form a color layerincluding a plurality of colored resists on a substrate in which awiring and a thin film transistor of amorphous silicon are formed.Further, in the color filter having a color layer including a pluralityof colored resists on a substrate, according to the present invention,is featured by that, for every colored resist of the plurality of thecolored resists except a last colored resist thereof, the step ofcoating the washed substrate with the colored resist, the step of dryingthe substrate under reduced-pressure condition to evaporate solventcontained in the colored resist and temporarily baking the substrate,the step of exposing the colored resist to print a pattern in thecolored resist, the step of developing the pattern, the step ofhardening the printed pattern to a hardness level, in which there is nodefect of a printed colored resist pattern in a resist printing step anda developing step, which are performed later, the step of repeating theabove mentioned steps and, for the last colored resist, in forming thelast colored resist pattern, the step of coating the washed substratewith the colored resist, the step of drying the substrate underreduced-pressure condition to evaporate solvent contained in the coloredresist and temporarily baking the substrate, the step of exposing thecolored resist to print a pattern in the colored resist, the step ofdeveloping the pattern, the step of hardening the printed pattern to ahardness level, in which there is no defect of a printed colored resistpattern in a resist printing step and a developing step, which areperformed later, and the step of simultaneously hardening all of thecoated colored resist patterns by not the hardening due to light andheat but a normal baking.

[0018] According to another embodiment of the present invention, a colorfilter having a light shield layer formed of light sensitive blackresist and a color layer including a plurality of colored resists, whichare formed on a substrate is provided. The light shield layer and therespective colored resists except a last colored resist are formed bythe step of coating the washed substrate with the colored resist, thestep of drying the substrate under reduced-pressure condition toevaporate solvent contained in the colored resist and temporarily bakingthe substrate, the step of exposing the colored resist to print apattern in the colored resist, the step of developing the pattern, thestep of hardening the printed pattern to a hardness level, in whichthere is no defect of a printed colored resist pattern in a resistprinting step and a step of developing, which are performed later, andthe step of repeating the above mentioned steps and, for the lastcolored resist, by the step of coating the washed substrate with thecolored resist, the step drying the substrate under reduced-pressurecondition to evaporate solvent contained in the colored resist andtemporarily baking the substrate, the step of exposing the coloredresist to print a pattern in the colored resist, the step of developingthe pattern, the step of hardening the printed pattern to a hardnesslevel, in which there is no defect of a printed colored resist patternin a resist printing step and a step of developing, which are performedlater the step of simultaneously hardening all of the coated coloredresist patterns by not the hardening due to light and heat but a normalbaking.

[0019] According to a further embodiment of the present invention, acolor filter having a color layer including a plurality of coloredresists and a transparent organic interlayer film formed of a negativetype resist, which are formed on a substrate, is featured by that therespective colored resist layers and the transparent organic interlayerfilm are formed by the step of coating the substrate, which is washed,with the colored resist, the step of evaporating solvent contained inthe colored resist by a reduced-pressure drying and a temporary baking,the step of exposing the colored resist to print a pattern therein, thestep of developing the printed pattern and hardening the colored resistpattern to a hardness level in which there is no defect of a printedcolored resist pattern in a resist printing step and a developing step,which are performed later, the step of repeating the above steps and,for the last colored resist, by the step of coating the substrate, whichis washed, with the colored resist, the step of evaporating solventcontained in the colored resist by a reduced-pressure drying and atemporary baking, the step of exposing the colored resist to print apattern therein, the step of developing the printed pattern andhardening the colored resist pattern to a hardness level in which thereis no defect of a printed colored resist pattern in a resist printingstep and a developing step, which are performed later and the step ofnormally baking all of the colored resist patterns simultaneously whenthe last transparent organic interlayer film is formed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a plan view of a substrate of a color filter accordingto the present invention;

[0021]FIG. 2 is a cross section taken along a line I-I in FIG. 1;

[0022]FIG. 3 is a flowchart showing a fabrication procedure of a colorlayer;

[0023]FIG. 4 shows a photo-curing step and a temporary post-baking stepof the fabrication procedure shown in FIG. 3;

[0024]FIG. 5 is a plan view of a TFT array substrate having a colorfilter layer formed thereon; and

[0025]FIG. 6 is a flowchart showing a conventional fabrication procedureof a color filter layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring to FIG. 1 and FIG. 2, a color filter according to thepresent invention includes a transparent substrate 201, a lightshielding layer 202 made of either metal or black resist formed on thetransparent substrate 201, a color layer including a red colored resist203, a green colored resist 204 and a blue colored resist 205, which areformed on the light shield layer 202, a transparent organic interlayerfilm 206 formed on the color layer and an opposing electrode 207 formedof a transparent electrically conductive material formed on thetransparent organic interlayer film 206.

[0027] The transparent substrate 201 may be made of any transparentmaterial provided that its physical properties and configuration are notchanged in a heat processing in a fabrication method. Glass, quartz orplastics may be used the transparent substrate 201. When the transparentsubstrate is used for a flat display panel, glass is generally used.

[0028] The light shield layer 202 is provided in order to prevent colorsof lights transmitted the filter from being mixed to thereby improvequality of the optical filter. Although, the light shield layer 202 isnot always necessary, the light shield layer 202 may be formed by usingphotolithography and etching of a metal layer of such as chromium havinglight shielding characteristics or by coating the substrate with lightsensitive black resist and exposing and developing with using a desiredpattern.

[0029] A material of the resist, which is differently colored in formingthe color layer, may be any, provided that its characteristics ischanged when irradiated with UV light. A negative type light sensitiveresist formed of light sensitive polyimide, PVA resin, light sensitiveacrylic resin or light sensitive epoxy resin is usually used as theresist material. A coating method of the resist is also any and thecoating is performed by, for example, a spin coat, a slit coat or acoating, etc.

[0030] In this embodiment, in order to prevent characteristics the colorlayer, that is, the colored resists from being changed or prevent thequality of the color layer from being degraded in the fabricating stepsafter the formation of the color layer, the color layer is coated thetransparent organic interlayer film 206 having high anti-chemicalscharacteristics as an overcoat film. When a patterning of the overcoatfilm 206 is unnecessary, the overcoat film may be formed by coating atransparent organic resist and baking it normally. When the patterningof the overcoat is necessary, the overcoat film 206 is formed byexposing and developing the substrate coated with a light sensitiveresist with using a desired pattern. In a case where the light sensitiveresist used for the overcoat film is colored, the normal baking isperformed after bleaching the light sensitive resist by exposing thedeveloped light sensitive resist.

[0031] Now, the fabrication procedure for the color layer including thecolored resists 203, 204 and 205 will be described with reference to theflowchart shown in FIG. 3.

[0032] After the washing step (step S1) of washing away extraneoussubstances adhered to the transparent substrate 202, the resist coatingstep (step S2) of coating the substrate with a light sensitive, firstcolored (red, for example) resist is performed. Then, thereduced-pressure drying step (step S3) of evaporating solvent containedin the red colored resist and the temporary baking step (step 4) areperformed. Then, the exposing step (step S5) of exposing the substrateto print a pattern and the developing step (step S6) of developing theprinted pattern are performed. Thereafter, the photo-curing step ofhardening the printed pattern formed by light and heat to a hardnesslevel in which the resist material is not solved in solvent used in acoating step to be performed later and the resist is not developed againin a second and subsequent developing steps and the temporarypost-baking step are performed (step S7), resulting in a desired firstcolored resist pattern. The second colored (green color, for example)resist pattern is formed by repeating the above mentioned steps (step S8to step S14). The third colored (blue color, for example) resist patternis formed through the steps S15 to S20, which are the same as the steps(step S8 to step S13) for the second colored resist pattern. The normalbaking step (S21) of completely hardening the resist patterns of allcolors (red, green and blue) is performed.

[0033] The washing steps (steps S1, S8 and S15) for the red, green andblue color resists are preferably performed before the resist coatingsteps, respectively. The washing step may be performed by brushing,ultrasonic washing or chemical washing using isopropanol, etc. However,for a color layer pattern whose surface and interface on the substrateside are hardened by a photo-curing step for surface hardening and athermal-curing step to be described later, it is preferable to wash itwith pure water whose physical defect is small. The drying of thesubstrate after washed is performed at 120 to 180° C. for 2 to 5 minutesby using an infrared (IR) heater or a hotplate, etc.

[0034] The resist material used in the respective resist coating steps(steps S2, S9, S16) is a negative type light sensitive colored resistsuch as light sensitive polyimide, PVA resin, light sensitive acrylicresin and light sensitive epoxy resin, etc. A coating method of theresist is also any and the coating is performed by, for example, a spincoat, a slit coat or a coating, etc.

[0035] The reduced-pressure drying step (step S3, S10, S17) immediatelyafter the resist coating step is to evaporate solvent contained in theresist and to make heat distribution uniform in the next temporarybaking step and an aimed reduced-pressure and an aimed drying time areset according to an amount of resist material and a content of solventthereof, etc.

[0036] The temporary baking step (step S4, S11, S18), is performed by ahotplate or an oven, etc., at 70˜100° C. for about 2˜4 minutes toevaporate a residual portion of the solvent in the resist after thereduced-pressure drying step.

[0037] The resist-coated substrate after the temporary baking step isexposed with a desired pattern in the exposing step (step S5, S12, S19).The exposing method may be any provided that the method denatures thelight sensitivity of the resist. For example, this is performed by usinga projection system using a mask or a laser drawing, etc. Light used inthis exposing step may be any provided that it includes a wavelength towhich the mask is sensitive. For example, ultraviolet ray, g, h or i rayof a mercury lamp, xenon lamp ray, excimer laser light, X ray, electronbeam, ray, ion beam, etc., may be used.

[0038] After the exposing step, the development is performed in thedeveloping step (step S6, S13, S20). The development is performed by amethod suitable for constituents of the resist with using a developer,which is generally as an organic alkaline solution or an inorganicalkaline solution, etc.

[0039] In the present invention, the color layer is not completelyhardened by the photo-curing and thermal hardening step for hardeningonly an upper surface of the color layer and an interface between alower surface of the color layer and the substrate. Therefore, theposition of the same step in the flowchart may be any. Alternatively,the hardening steps for the three colored resists may be performedsimultaneously. The photo-curing portion of the photo-curing andtemporary post-baking step (step S7, S14) performed by light irradiationof the present invention is to harden the upper surface of the colorlayer pattern in order to prevent succeeding color pigment and developerfrom soaking into the color layer. On the other hand, the temporarypost-baking portion of the photo-curing and temporary post-baking step(step S7, S14) is to process the interface portion between the colorlayer pattern film obtained by the developing step and the underlyingsubstrate such that a soaking of a succeeding color pigment and asucceeding developer into the color layer from the interface and apeeling-off of the color layer from the substrate is prevented.

[0040] The photo-curing and temporary post-baking (thermosetting) stepaccording to the present invention will be described in detail withreference to FIG. 4. In FIG. 4, a light shield film 302 is formed on asubstrate 301 and a first color layer patterning film 304 is formed onthe light shield film 302 through the developing step. In thephoto-curing step (step S7, S14), a surface of the color layerpatterning film 304 on the substrate 301 is irradiated with light 401 toharden a portion of the resist in the vicinity of the surface thereofirradiated with the light to a hardness level in which any abnormalitydoes not occur in later steps. A light source to be used in thephoto-curing step is similar to that used in the exposing step, providedthat the light has a wavelength to which the resist is sensitive.Preferably, the light source used in the exposing step is also used inthe photo-curing step in view of reduction of the fabrication cost. Inthis embodiment, the photo-curing step is performed by a simultaneousirradiation of normal pressure ultraviolet ray under a condition ofabout 1000 mj/cm². This condition is preferably 5˜10 times theappropriate amount of exposure when the color layer pattern is exposed.In the above mentioned condition, the time required is only about oneminute. By performing the photo-curing step, only the surface portion ofthe color layer pattern is hardened, so that it is possible to preventthe soaking of the developer, etc., from the surface portion in latersteps. Compared with the conventional temporary baking step using anoven, the increasing time of temperature and the decreasing time oftemperature become unnecessary, so that it becomes possible toeffectively harden only the surface portion of the color layer within ashort time.

[0041] Further, the temporary post-baking (simple thermosetting) step(step S7, S14) in the present invention is performed under the conditionthat the resist 304 formed on the substrate 301 is hardened to ahardness level in which the adhesiveness in the interface between theresist 304 and the substrate 301 is improved and the inconvenience suchas soaking of developer into the interface in later steps does notoccur. This heat-treatment is preferably performed by heating a rearsurface of the substrate 301 with using a hotplate 400 shown in FIG. 4.The heating is performed under a condition of 120˜150° C. for about 2˜5minutes. When the hotplate is used in lieu of an oven, it is possible tosubstantially reduce the increasing and decreasing times of temperature,compared with the case of the oven. Further, since the hotplate used inthe drying step after the washing step of the substrate can be used asit is, it is possible to effectively use the merits of the hotplate,that is, compactness and low cost. Further, since the hotplate 400 isarranged below the rear or lower surface of the substrate 301 to heatthe substrate as shown in FIG. 4, it is possible to easily harden thesurface (interface) of the color layer 304 within a short time and toincrease the adhesion force of the color layer to the substrate withinthe short time. Needless to say, the lower surface (interface) of thecolor layer 304 opposing to the light shielding film pattern 302 is alsoeasily hardened within the short time.

[0042] The normal baking step (step S21) for simultaneously baking thecolored resists normally after the last developed pattern among theplurality of the resist patterns is formed is executed at about 200˜230°C. for about 1 hour by using a hotplate or an oven, etc. By this step,it is possible to prevent inconvenience of such as gas generation from avolatile material during a heat treatment in forming such as thetransparent organic interlayer film 206 in the later step.

[0043] In the previously mentioned JPH11-337724A, after the exposing ofthe colored resist layer, the coated resist layer is hardened to ahardness level in which defect such as peeling-off of the resist layerdoes not occur in the developing step of the resist layers of othercolors formed subsequently. In detail, the heat treatment is performedat 80˜100° C. for 5˜15 minutes (preferably, 90° C. for 10 minutes) byusing a hotplate, an oven or infrared ray irradiation, etc. In thisembodiment, however, the photo-curing step for hardening the uppersurface of the color layer and the temporary post-baking step (lightirradiation step and the simple thermal curing step) for hardening thelower surface (interface) of the color layer on the side of thesubstrate are used in the formation of the first and second coloredresists. Therefore, the necessary and sufficient processing time toharden the surface becomes as short as about 20˜40 minutes. Accordingly,it becomes possible to substantially reduce the overall fabrication timeto thereby improve the producibility and reduce the stockpile in thestep.

[0044] Incidentally, JPH8-194109A discloses a technique in which,instead of a heat-curing processing of the color pixel image obtainedafter the development, a photo-curing processing by means of an exposingdevice is used in at least one of the three steps except the last stepamong four steps for forming the black, red, green and blue color pixelimages of the color filter fabrication method. In the disclosedtechnique, there is a description summarized as that, by employinganti-solvent photo-polymerizing constituents, the color pixel image,which is durable against a later coating of photo-polymerizingconstituents, can be formed. That is, according to the disclosedtechnique, only the photo-curing by means of an exposing device isperformed in the step corresponding to either the step S7 or the stepS14 shown in FIG. 3. However, the prior art does neither disclose norsuggest the present invention in which not only the photo-curing butalso the heat-curing for hardening only the surface of the color layeron the side of the substrate are used. Further, in the disclosed priorart, hardness of a portion of the color layer in the vicinity of theinterface between the color layer and the substrate is insufficient andthe improvement of the adhesion force obtainable by the presentinvention can not be expected though the effect of shortening of time islarge compared with the case where the temporary post-bake step isemployed. Further, since a special material is used for the color pixelimage, the generality is low. Although the heat-curing processing afterthe developing processing is removed, very specific photo-polymerizingconstituent is required. Therefore, realization of the disclosedtechnique is difficult by using commercially available resist material.Particularly, in order to obtain an intimate contact between thesubstrate and the color layer by light, the resist must be transmissivefor the light. Since well known economical resist material can not beused, increase of fabrication cost is unavoidable. Particularly, for theblack resist, light does not reach the interface between the substrateand the resist, it is difficult to obtain an intimate contact of theresist to the substrate.

[0045] In the present invention, however, it is possible to reduce thefabrication time and to restrict the increase of fabrication cost evenwhen the conventional color resist is used. That is, in the presentinvention, in order to prevent the developer, etc., from soaking intothe surface of the color layer and the interface between the color layerand the substrate in the next step, the hardening of the upper surfaceof the color layer is performed by using the light irradiation means andthe lower surface thereof on the side of the interface is hardened byusing the heat-curing means, so that the merit and demerit arecompensated for, complementarily.

[0046] In this embodiment, it is possible, compared with the case whereeither one of the photo-curing and the heat-curing is performed, toimprove the adhesiveness of the color layer (color resist pattern) tothe transparent substrate 201 by using the photo-curing for hardeningonly the upper surface of the color layer and the heat-curing (temporarypost-baking) for hardening only the lower surface of the color layer onthe side of the substrate. Therefore, in forming another colored resistpattern, it is possible to not only prevent the developer used in thedeveloping step from soaking into the surface of the colored resistpattern but also reliably prevent the developer from soaking intobetween the colored resist pattern and the transparent substrate 201.Since these effects can be achieved together with the shortening effectof the fabrication time, the utility of the present fabrication methodis very high.

[0047] Now, a second embodiment of the present invention will bedescribed with reference to FIG. 5.

[0048] In the first embodiment, the color filter layer is formed on theusual transparent substrate. However, the present invention can beapplied to a formation of a color filter layer on a thin film transistor(TFT).

[0049] In a TFT array substrate shown in FIG. 5, TFT's are formed bywiring portions 502 and amorphous silicon (a-Si) portions 503 formed ona transparent substrate 501. Metal film of such as chromium used as thewiring 502 is formed by sputtering, etc., and the a-Si portions 503 areformed by CVD, etc. On the TFT array substrate, a color layer composedof colored resists 504, 505 and 506 is formed along a fabricationprocedure similar to that used in the first embodiment. A light shieldlayer 507 is formed of a metal or a black resist on the colored resists504, 505 and 506 and, after a transparent organic interlayer film 508 isformed, pixel electrodes 509 of transparent conductive film are formed.

[0050] By forming the red colored resist 504, the green colored resist505 and the blue colored resist 506 on the transparent substrate havingthe TFT's each including the wiring 502 and the a-Si portion 503 formedthereon, according to a procedure similar to that used in the firstembodiment, it is possible to improve the adhesiveness of the colorlayer to the transparent substrate 501. Therefore, it is possible toprevent, in forming another colored resist pattern, the developer usedin the developing step from soaking into between the colored resistpattern and the transparent substrate 501.

[0051] It should be noted that, although the preferred embodiments havebeen described, the present invention is not limited thereto and thepreferred embodiments can be modified in various manners within thescope of the present invention. For example, when a light sensitiveblack resist is used as the light shield layer 202, it may be possibleto harden only surface portions of the light shield layer 202, the firstcolored resist pattern and the second colored resist pattern by thephoto-curing and the temporary post-baking and to completely harden themat the same time when the third colored resist pattern is formed, by thenormal baking step. When a negative type resist similar to the colorlayers is used for the transparent organic interlayer film 206, it maybe possible to harden only surface portions (including the interface tothe substrate) of the first colored resist pattern, the second coloredresist pattern and the third colored resist pattern by the photo-curingand the temporary post-baking and then to completely harden them at thesame time when the transparent organic interlayer film 206 is formed, bythe normal baking step. Further, it may be possible to harden onlysurface portions (including the interfaces to the substrate) of thelight shield layer 202, the first colored resist pattern, the secondcolored resist pattern and the third colored resist pattern by thephoto-curing and the temporary post-baking and then to completely hardenthem at the same time when the transparent organic interlayer film 206is formed, by the normal baking step.

[0052] As described hereinbefore, in the steps for forming the colorlayers other than the last color layer forming step, only the surfaceportions (including the interface portions to the substrate) of thecolor layers other than the last color layer are hardened to a hardnesslevel, in which there is no defect of the coated colored resist patternsin the resist coating step and the developing step, by the photo-curingstep and the temporary post-baking step, instead of the normal baking.Therefore, the necessary and sufficient hardening processing can becompleted within a time as short as about 20˜40 minutes. Accordingly, itis possible to substantially reduce the fabrication time to therebyimprove the producibility and reduce the stock in the respective steps.In addition, it is possible to improve the adhesiveness of the coloredresist patterns to the substrate. Therefore, it is possible to prevent,in forming another colored resist pattern, the developer used in thedeveloping step from soaking into between the colored resist pattern andthe transparent substrate.

What is claimed is:
 1. A color layer forming method for forming a colorlayer composed of a plurality of colored resists, comprising: a firststep of forming a first colored resist pattern on a substrate by coatingthe substrate with a first colored resist, exposing the first coloredresist to print the first colored resist pattern and developing thefirst colored resist; a second step of hardening only a surface portionof said first colored resist pattern by irradiating said surface portionwith light; a third step of thermally curing a surface portion of saidfirst colored resist pattern on the side of said substrate by heatingsaid surface portion; and a baking step of baking the first coloredresist pattern formed on said substrate in a last step, temperature inthe baking step being higher than temperature used in the third stepsuch that the whole portion of the first colored resist pattern havingthe hardened surface portions are simultaneously hardened.
 2. A colorlayer forming method as claimed in claim 1, wherein the light used inthe second step is a light from an exposing light source used in thefirst step and the third step is performed by using a local heat sourcearranged on a side of said substrate opposing to said colored resistpattern and heating said substrate.
 3. A color layer forming method asclaimed in claim 1, further comprising the step of repeating the firstto third steps, wherein the resist pattern in the last step is coloredby other color than that of the first colored resist.
 4. A color layerforming method as claimed in claim 1, further comprising a step ofrepeating the first to third steps while changing color of the coloredresist, wherein the resist pattern in the last step is an overcoat film.5. A color layer forming method as claimed in claim 1, furthercomprising a step of repeating the first to third steps, wherein saidfirst colored resist is black colored.
 6. A color layer forming methodas claimed in claim 1, wherein the first step is performed for each of aplurality of colored resists and comprises a resist coating step ofcoating a washed substrate with respective colored resists, areduced-pressure drying and temporary baking step of evaporating solventcontained in the respective colored resists, an exposing step ofexposing the substrate to print resist pattern and a developing step ofdeveloping the printed pattern, the second and third steps are aphoto-curing step of hardening only a surface portion of the coloredresist pattern by light and heat to a hardness level, in which there isno defect of the coated colored resist patterns in the resist coatingstep and a developing step to be performed later, and a temporary bakingstep for hardening a surface portion of the colored resist pattern onthe side of the substrate, respectively.
 7. A color layer forming methodas claimed in claim 1, wherein a wiring and thin film transistors formedof amorphous silicon are preliminarily formed on the substrate.
 8. Acolor layer forming method for forming a color layer including aplurality of colored resists on a substrate, comprising: a first resistcoating step of coating the substrate with a first colored resist; afirst evaporation step of evaporating solvent contained in the firstcolored resist after the first resist coating step; a first exposingstep of printing a pattern in the first colored resist after the firstevaporation step; a first developing step of forming the first coloredresist pattern by developing the pattern printed in the first coloredresist after the first exposing step; a first photo-curing step ofhardening at least a surface of the first colored resist pattern; afirst temporary baking step of hardening at least a lower surface of thefirst color layer by heat; a second resist coating step of coating thesubstrate having the first color layer pattern with a second coloredresist after the first photo-curing step and the first temporary bakingstep; a second evaporation step of evaporating solvent contained in thesecond colored resist after the second resist coating step; a secondexposing step of printing a pattern in the second colored resist afterthe second evaporation step; a second developing step of forming thesecond colored resist pattern by developing the pattern printed in thesecond colored resist after the second exposing step; a secondphoto-curing step of hardening at least a surface of the second colorlayer pattern; a second temporary baking step of hardening at least alower surface of the second color layer by heat; a third resist coatingstep of coating the substrate having the first color layer pattern andthe second color layer pattern with a third colored resist after thesecond photo-curing step and the second temporary baking step; a thirdevaporation step of evaporating solvent contained in the third coloredresist after the third resist coating step; a third exposing step ofprinting a pattern in the third colored resist after the thirdevaporation step; a third developing step of forming the third coloredresist pattern by developing the pattern printed in the third coloredresist after the third exposing step; and a normal baking step ofhardening the first colored resist pattern, the second colored resistpattern and the third colored resist pattern by simultaneously heatingthe first to third colored resist patterns at a temperature higher thantemperatures in the first to third temporary baking steps.
 9. A colorfilter forming method using the color layer forming method as claimed inclaim 8, further comprising a step of forming a light shield layer oflight sensitive black resist on said substrate, wherein all coatedcolored resist patterns including the light shield layer aresimultaneously hardened in the normal baking step.
 10. A color filterforming method using the color layer forming method as claimed in claim8, further comprising a third photo-curing step of hardening at least asurface of the third colored resist pattern before the normal bakingstep and a third temporary baking step of hardening at least a lowersurface of the third colored resist pattern by heat, the normal bakingstep being performed after an overcoat layer is formed on the first tothird colored resist patterns after the third temporary baking step. 11.A color filter formed by the color layer forming method as claimed inclaim 8.